PwrGSD (version 2.3.8)

Haybittle: The Haybittle method of Boundary Construction

Description

The function Haybittle is used in calls to the functions GrpSeqBnds and PwrGSD as a possible setting for the argument EfficacyBoundary. NOTE: the Haybittle method is not implemented as a futility boundary method The Haybittle method is one of four currently availiable choices (efficacy only), the others being LanDemets, SC (stochastic curtailment), and user specified.

Usage

Haybittle(alpha, b.Haybittle, from = NULL, to = NULL)

Value

An object of class boundary.construction.method which is really a list with the following components. The print method displays the original call.

type

Gives the boundary construction method type, which is the character string "Haybittle"

alpha

The numeric value passed to the argument 'alpha' which is the total probability of type I error.

b.Haybittle

The numeric value passed to the argument 'b.Haybittle' which is the user specified efficacy boundary at all but the last analysis.

from

Description of 'comp2'

to

You're not using this, right?

call

see above.

Arguments

alpha

The total probability of type I error.

b.Haybittle

User specified efficacy boundary at all but the last analysis.

from

WARNING EXPERIMENTAL: See the documentation under LanDemets or SC. I'm not quite sure if this works or even makes sense. Don't use it, ok?

to

See above.

Author

Grant Izmirlian

Details

The Haybittle approach is conceptually the simplest of all methods for efficacy boundary construction. However, as it spends nearly no alpha until the end, is for all practical purposes equivalent to a single analysis design and to be considered overly conservative. This method sets all the boundary points equal to b.Haybittle, a user specified value (try 3) for all analyses except the last, which is calculated so as to result in the total type I error, set with the argument alpha.

References

see references under PwrGSD

See Also

LanDemets, SC, GrpSeqBnds, and PwrGSD

Examples

## example 1: what is the result of calling a Boundary Construction Method function
    ## A call to 'Haybittle' just returns the call
    Haybittle(alpha=0.05, b.Haybittle=3)
    
    ## It does arguement checking...this results in an error
    if (FALSE) {
      Haybittle(alpha=0.05)
    }
    
    ## but really its value is a list with the a component containing
    ## the boundary method type, "LanDemts", and components for each
    ## of the arguments.
    names(Haybittle(alpha=0.05, b.Haybittle=3))

    Haybittle(alpha=0.05, b.Haybittle=3)$type
    Haybittle(alpha=0.05, b.Haybittle=3)$alpha
    Haybittle(alpha=0.05, b.Haybittle=3)$b.Haybittle
    Haybittle(alpha=0.05, b.Haybittle=3)$call

## example 2: ...But the intended purpose of the spending functions 
## is in constructing calls to 'GrpSeqBnds' and to 'PwrGSD':
     

    frac <- c(0.07614902,0.1135391,0.168252,0.2336901,0.3186155,
              0.4164776,0.5352199,0.670739,0.8246061,1)

    test <- GrpSeqBnds(frac=frac, EfficacyBoundary=Haybittle(alpha=0.025, b.Haybittle=3))